Y-PARAMETER of Two Port Network

In this article we will study about Y Parameter of two port network.

Y-Parameter is also called "Short Circuit Parameter" and "Admittance Parameter".
In Y-Parameter, the input and output currents are function of input and output Voltages.
( I1 , I2 ) = f ( V1 , V2 )
It can also be written as:
[I] = [Y]   [V]
where [Y] represents Admittance Matrix.
In matrix form,
[I1] =    [Y11  Y12]   [V1]
[I2] =    [Y21  Y22]   [V2]
Writing it in equation,
I1 = Y11* V1 + Y12* V2 .........eq1
I2 = Y21* V1 + Y22* V2 .........eq2
CASE-1 SHORT CIRCUITING THE OUTPUT PORT
If the Output port of the two port network is  short circuited then output voltage is zero, i.e. V2 = 0.

Now, equation 1 and 2 will be reduced to :
I1 = Y11* V1
I2 = Y21* V1
So, Y11 = I1 /V1    ( keeping v2 = 0 )
      Y21 = I2/ V1    ( keeping V2 = 0 )
CASE-2 SHORT CIRCUITING THE INPUT PORT
If the Input port of the two port network is short circuited then the input voltage is zero, i.e. V1 = 0.

Now, equation 1 and 2 will be reduced to :
I1 = Y12* V2
I2 = Y22* V2
So, Y12 = I1/ V2    ( keeping V1= 0 )
       Y22 = I2/ V2  ( keeping V1 = 0 )
Y11 is called input driving point Admittance.
Y12 is called forward transfer Admittance.
Y21 is called reverse transfer Admittance
Y22 is called output driving point Admittance.
For a network to be symmetrical , Y11 = Y22
For a network to be reciprocal, Y12 = Y21
EQUIVALENT CIRCUIT OF Y-PARAMETER